Pressure-operated device for clamping of workpieces on gear processing machines

ABSTRACT

A device for clamping workpieces on gear processing machines in which a drawbar is driven axially to pull to workpiece onto a workpiece support. A resilient collet is secured to a drawbar and has an outer cone for engaging a draw-in arbor to permit the drawbar to apply an initial pressure on the workpiece when the drawbar is pulled toward a workpiece support. The collet is received by a countercone which resiliently yields to the pull of the drawbar to permit the drawbar to apply a final clamping pressure to the workpiece.

United States Patent Fischer 154] PRESSURE-OPERATED DEVICE FOR CLAMPINGOF WORKPIECES ON GEAR PROCESSING MACHINES [72] Inventor: Heinrich R.Fischer, Munich, Germany [73] Assignee: Carl Harth, Maschinen-undZahru'adfabrik, Munich, Germany [22] Filed: July 22, 1969 [21] Appl.No.: 843,650

[30] Foreign Application Priority Data July 30, 1968 Germany ..P 17 52877.7

[52] US. Cl. .90/l, 90/11 A, 279/51 [51] Int. Cl. ..B23f 23/06 [58]Field of Search ..90/l, 88, 11 A, 11 R; 82/44;

[56] References Cited UNITED STATES PATENTS Meinke ..90/ l l A 1 May 23,1972 2,113,124 4/1938 Zimmermann ..90/1X 3,474,705 10/1969 Jacob, Jr..90/11 A FOREIGN PATENTS OR APPLICATIONS 21,7-19 8/196l Germany ..90/1

' Primary Examiner-Gil Weidenfeld AttOmey-Woodhams, Blanchard and Flynn[57] ABSTRACT A device for clamping workpieces on gear processingmachines in which a drawbar is driven axially to pull to workpiece ontoa workpiece support. A resilient collet is secured to a drawbar and hasan outer cone for engaging a draw-in arbor to permit the drawbar toapply an initial pressure on the workpiece when the drawbar is pulledtoward a workpiece support. The collet is received by a counterconewhich resiliently yields to the pull of the drawbar to permit thedrawbar to apply a final clamping pressure to the workpiece.

. 2 C 5 Figu e PATENTEUMM 23 1972 3,664. 227

SHEET 2 OF 4 PRESSURE-OPERATED DEVICE FOR CLAMPING OF WORKPIECES N GEARPROCESSING MACHINES The invention relates to a pressure-operated devicefor the clamping of workpieces into gear processing machines in whichthe workpiece is located on a workpiece support by an axially drivabledrawbar and the workpiece is thereby centered.

It is also known to have workpieces having a central bore clampedbetween a rotatably drivable rotary table and a clamping member on gearprocessing machines, namely, with a drawbar which is connectible to thetailstock spindle sleeve through an expandable sleeve by means of aclamping piston having conical surfaces, the sleeve being expandableagainst the force ofa spring (U.S. Pat. No. 3 200 71 l).

The conical surface on the clamping piston which effects an expanding ofthe sleeve so that its cylindrical outer surface is urged against acylindrical inner surface, requires a sharply tapered draw-in arbor.However, very often workpieces with a small opening therein are to beclamped by a relatively large pressure. If one would taper the draw-inarbor according to the earlier teaching for forming a clamping piston,then the remaining cross section would not be sufficient for therequired clamping pressure.

The purpose of the invention is to produce a pressureoperated clampingdevice of the above-discussed type which is suitable for workpieceshaving a relatively small center bore.

The basic purpose of the invention is attained by a presently knowncollet, which is closable against a spring tension and has an outerconical surface for clamping a draw-in arbor for pressing either theworkpiece or a workpiece engaging clamp, which collet is received in aconically shaped opening which can be urged resiliently in direction ofthe drawbar pull. The invention does not depend on the direction inwhich the drawbar acts. Thus the workpiece can, for example, be pulledonto the workpiece support on the workpiece spindle or the like or alsoonto a countersupport in a direction which is either downwardly,upwardly or to the side.

If the draw-in arbor or the workpiece does not allow any adjustment, theinvention is further constructed so that the drawin arbor or theworkpiece are forceably clamped by the collet.

If, however, on the other hand, the friction in the frictionalconnection is not sufficient for the clamping force, the invention isfurther constructed so that the draw-in arbor may be provided with ashoulder or a notch or the like so that same is positively clamped bythe collet. It is an advantage of the invention, that the positivelocking can be effected by a very small shoulder of, for example,approximately a few tenths of a millimeter, which shoulder thus does notappreciably weaken the draw-in arbor or the workpiece.

Furthermore, a construction of the subject matter of the invention isadvantageous in which the draw-in arbor is secured to a presently knowncountersupport.

Advantageous for centering the workpiece in the device of the inventionis the construction of a resilient centering device which is supportedin the collet.

Furthermore, depending on the use, two further constructions of theinvention are advantageous, namely, one being that the collet ispositively connected to the drawbar in both directions of movement, andthe other one being that a collet having some axial movement isconnected to the drawbar.

Further advantages and characteristics of the invention will bedescribed in the following description.

The invention is discussed in connection with some exemplary embodimentswhich are illustrated in FIGS. 1 to 5.

FIG. 1 illustrates a gear generating machine on which the invention can,for example, be utilized.

FIG. 2 illustrates schematically in a cross-sectional view one exemplaryembodiment of the invention.

FIG. 3 is an enlarged fragmentary view of the device of FIG. 2 but withthe parts in a different working position.

FIG. 4 illustrates another exemplary embodiment of the invention.

FIG. 5 illustrates a further exemplary embodiment of the invention.

FIG. 1 is illustrative of a gear generating machine for making gears onwhich the invention can be utilized. The invention can also be used onother types of generating machines. A workpiece carriage 11 is supporteddrivably, movably and, if necessary, securably on a machine frame 10. Asupport 12 is secured to the workpiece carriage and supports a tailstockl3. Said tailstock is supported for such movement, driving or securementwith respect to the support 12 as desired. Furthermore, a workpiecespindle is supported drivably and rotatably in a known manner in theworkpiece carriage. The spindle'of the headstock is identified at 14. Aworkpiece 15 is clamped between said spindle and the tailstock. Thetailstock has for this purpose in the exemplary embodiment a rotatablespindle sleeve 16 and the headstock spindle is provided with a workpiecesupport 20 which will be referred to hereinafter as a bell 20.Furthermore, a worktool carriage 17 is supported movably and drivably ina known manner on the machine frame. The worktool carriage is providedwith a swingable worktool holder 18. Said holder supports in a knownmanner a worktool 19 which, in the illustrated embodiment, is a hob.

The above-described machine is known. The workpiece spindle 14 is, forexample, provided with a hydraulic clamping device which is also knownand is therefore not illustrated in detail.

A draw-in arbor 21 (FIG. 2) is screwed to the spindle sleeve 16.Furthermore, a clamp 23 is secured to a flange 22 of the draw-in arbor(as shown) or directly to the draw-in arbor. The clamp serves thepurpose of pressing the workpiece 15 onto a support 24 which is screwedto the top side of the bell 20. The support 24 is provided with adownwardly resilient ejector member 25 which, driven by springs 26,ejects the workpiece upwardly after the pressure of the clamp 23 hasbeen removed. The upward stroke of the ejector is limited by abutmentbolts 27. The bell 20 is secured to the headstock 14 by screws 40 and issecured by suitable means, for example, a block 41, against rotationrelative to the headstock. The aforementioned draw-in arbor centersaccording to the invention I the workpiece in an opening 28 therethroughand is used at the same time as a tensioning means in the mannerdescribed hereinafter.

A receiving ring 30 is movably guided, according to the invention, in aninternal recess 29 in the bell 20. The receiving ring 30 is pressedupwardly against a shoulder 32 (FIG. 3) by springs 31. The springs3l aresupported on a flange 33 which is secured to the bell 20 by screws (FIG.2). The receiving ring 30 is secured against rotation by pins 34. Thereceiving ring 30 is provided with a conically shaped central opening 35which enlarges in an upward direction. A collet 36 which, in a knownmanner, is provided with slots 37 so that the receiving bore 38 of thecollet can be expanded resiliently, is arranged concentrically to thereceiving ring 30 or to the headstock 14. The collet 36 is provided atits upper end with a conical surface 39 which fits into theaforementioned conically shaped central opening 35. The collet 36 isthreadedly engaged with adrawbar 42 which, in a known manner, can bemoved axially by a clamping device, for example, a hydraulic clampingpiston. The hydraulic clamping piston is illustrated schematically inFIG. 2 in a reduced scale and is identified at 43.

Before a workpiece is clamped, the tailstock 13 and the draw-in arbor 21are moved upwardly. The collet 36 is raised, as illustrated in FIG. 3.The receiving ring 30 engages the shoulder 32 under the pressure of thesprings 31. The upper edge 44 of the ejector 25 is positionedapproximately at the height of the upper edge 45 of the support. Beforeclamping, the workpiece is placed on the upper edges 44, 45 of theejector 25; the tailstock I3 is then lowered until the draw-in arbor 21extends into the receiving bore 38 of the collet (dotted lines in FIG.3). The workpiece is thereby positioned as approximately illustrated inFIG. 2. The clamping piston 43 is then moved downwardly. The bore 38 inthe collet 36 slides over the outer surface of the arbor 21 firstwithout a clamping friction contact but with sufficient friction to pullpreferably the tailstock 13 or the clamp 23 onto the workpiece 15 toclamp the workpiece onto the support with a relatively small pressure.When the conical surface 39 engages the conically shaped opening 35,upon a further pulling of the drawbar 42, the upper end of the collet 36is compressed to engage the outer surface of the arbor 21 and thereceiving ring 30 is urged resiliently downwardly. A space 46 is formedthereby between the receiving ring 30 and the shoulder 32. A very tightclampin g is achieved hereby according to the invention whereby theclamping is not done by a pressure applied to the tailstock, which wouldresult in a jamming of the tailstock, but the clamping is caused bypulling the tailstock 13 toward the workpiece spindle 14. This resultsin a good connection between the workpiece carriage 11, the support 12,the tailstock 13, the workpiece 15, the bell and the workpiece spindle14. This good connection is achieved according to the invention by apure frictional connection between the draw-in arbor 21 and collet 36.Through this it is possible, even in the case of a small bore 28 in theworkpiece, to exert or to transmit a large clamping pressure through thedraw-in arbor which, according to the invention, centers the workpieceat the same time.

FIG. 4 illustrates an exemplary embodiment in which the tailstock 13 isnot pulled to the workpiece support but, instead, the workpiece is,according to the invention, pulled onto the workpiece support, wherebythe tailstock 13 is used as a support. The workpiece 50 is, for example,a gear block, namely a shaft with several ring gears 50/1, 50/2, 50/3.The workpiece 50 can, if desired, appear differently than the chosenexample. The workpiece is centered in the tailstock spindle sleeve 51with a known resilient footstock center. For pressing the workpieceagainst the hereinafter-described workpiece support, a clamp 53 is usedwhich is screwed to the spindle sleeve. Again a bell 54 is used as theworkpiece support, said bell being screwed onto the headstock 14' andfixed against rotation relative to said headstock 14 by suitable means.A support 55 which is adjusted to the workpiece is mounted on the bell54, the workpiece extending into said support with a smooth pin 50/4.

The support 55 has a cylindrical guide opening 56 which receives asleeve 57 which is guided for longitudinal movement. The sleeve 57 isurged toward the tailstock 13' by means of springs 58. The sleeve 57 issupported by means ofa flange 59 engaging a suitable shoulder 60 in thebell 54. A support flange 61 is secured to the bell 54 and is used as anabutment for the springs 58. The sleeve 57 can be urged resilientlydownwardly. The sleeve 57 is provided with a conically shaped opening 62at its upper end. A collet 63 is guided for longitudinal movement in thesleeve 57 or in the flange 59 or in another suitable part. The collet 63is provided with an outer conical surface 64 at its upper end, saidouter conical surface fitting into the conically shaped opening 62. Thecollet 63 is, as aforedescribed, slotted at the upper end so that it canexpand and contract resiliently. The collet 63 is provided with a flange65 at its lower end, which flange is inserted in a recess in aconnecting piece 66. The connecting piece 66 is, for reasons ofinstallation, composed of two parts, namely of a connecting cone 67 anda clamping nut 68. The flange 65 of the collet 63 is positionedaccording to the invention between these two parts with clearance enoughto move slightly axially. The connecting cone is threadedly engaged withthe drawbar 42 of the clamping device.

A resilient centering piece is provided in the collet 63. This centeringpiece can be a resilient footstock center or a centering bolt 69 whichis urged toward the workpiece by means of a spring 70 which is supportedon the collet 63 by means of a stopping member 71. At the end of theworkpiece 50 the centering bolt is provided with a centering ball 72which is urged toward the workpiece 50 by means ofa spring 73. The ballis secured against removal by any suitable means.

The operation of the device corresponds to the one of the earlierexemplary embodiment in such a manner that the connection between theworkpiece 50 and the bell 54 or the workpiece spindle 14 is positive,whereby the frictional connection is reinforced according to theinvention during the pulling of the drawbar 42' through theinterconnected conical surfaces 62, 64. It is important for theinvention that the sleeve 57 can be urged resiliently downwardly.Differing from the earlier embodiment, the drawbar 42 does not pull thetailstock 13 downwardly through a draw-in arbor but pulls the workpieceonto its support. An advantage which is decisive for the invention isthat the workpiece does not require a shoulder for clamping.

FIG. 5 illustrates one embodiment of the invention which is of animportance if a frictional connection between the drawin arbor and thecollet 36 is not sufficient for a required clamping pressure. In thisembodiment, all parts are constructed approximately in the same manneras, for example, in the embodiment of FIGS. 2 and 3. Only the draw-inarbor 80 is constructed differently, namely, it has a small enlargementat its lower end which is enlarged in FIG. 5 and identified withreference numeral 81. It is an advantage of the invention that only afew tenths of a millimeter of a difference in diameter are suflicient toeffect a positive connection. Thus, during clamping, the collet 36 fallsin behind the enlargement 81 and pulls the arbor 80 downwardly, as abovedescribed. Due to the conical surfaces 35, 39 and the urging of sameresiliently downwardly, a very tight connection is obtained according tothe invention.

In the exemplary embodiments the clamping axis (workpiece axis) isvertically oriented and the workpiece is pulled downwardly onto thesupport. The invention is not limited to this; but, for example, ahorizontal or otherwise directed clamping axis may be provided. It isalso possible to press or pull the workpiece against a plate which, forexample, is positioned above the workpiece. The invention is also notlimited to gear generating machines but can be used on all gearprocessing machines.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A workpiece clamping device, comprising:

a workpiece support engageable with one end of said workpiece;

a movable support member and means for moving same toward and away fromsaid workpiece support and engageable with the opposite end of saidworkpiece;

a drawbar and means for driving same axially toward and away from saidworkpiece;

clamping means on said drawbar for effecting, both an initial and afinal clamping coupling of said drawbar with said workpiece to pull saidworkpiece toward said workpiece support to thereby clamp said workpieceon said workpiece support; and

means for resiliently yielding to the movement of said drawbar to delaythe application of said final clamping coupling of said drawbar withsaid workpiece to thereby permit an adjusting movement of said workpiecerelative to said workpiece support prior to the application of saidfinal clamping coupling.

2. A workpiece clamping device comprising:

a workpiece support engageable with said workpiece;

arbor means arranged axially of said workpiece;

a clamping collet member adapted to engage said arbor means, saidclamping collet member having a first conical surface thereon;

means for causing a relative movement between said arbor means and saidclamping collet member;

a sleeve member having a second conical surface thereon cooperable withsaid first conical surface to cause said clamping collet member toengage said arbor means, said sleeve member being supported for axialmovement relative to said clamping collet" member to cause said clampingcollet member to first apply an initial clamping pressure on said arbormeans when a relative movement occurs between said arbor means and saidclamping collet member; and

resilient means for causing said sleeve member to resiliently resist therelative movement between said clamping collet member and said arbormeans to cause said clamping collet member to apply a final clampingpressure on said arbor means.

3. A workpiece clamping device according to claim 2, including a supportmember and means for moving same toward and away from said workpiecesupport; and

wherein said arbor means is secured to said support member.

4. A workpiece clamping device according to claim 3, wherein saidsupport member is rotatably secured in a tailstock movable toward andaway from said workpiece support.

5. A workpiece clamping device according to claim 2, including meanssupporting said arbor means for longitudinal movement relative to saidworkpiece support; and

wherein said arbor means is rotatably secured in a tailstock.

6. A workpiece clamping device according to claim 2, wherein saidclamping collet member has a plurality of angularly spaced slotsextending parallel to the longitudinal axis thereof.

7. A workpiece clamping device according to claim 2, wherein said arbormeans includes an enlargement engageable with said clamping colletmember to urge said cooperable conical surfaces tightly together toeffect a final clamping pressure of said clamping collet member on saidarbor means.

8. A workpiece clamping device according to claim 2, wherein said arbormeans is an elongated extension of said workpiece; and

wherein said clamping collet member is adapted to engage said elongatedextension of said workpiece.

9. A workpiece clamping device according to claim 8, including anelongated centering device supported for axial movement relative to saidclamping collet member.

10. A workpiece clamping device according to claim 2, wherein said meansfor causing a relative movement between said arbor means and saidclamping collet member is a drawbar drivable axially of said workpiece;and

wherein said clamping collet member is connected positively to saiddrawbar and is movable therewith.

11. A workpiece clamping device according to claim 2, wherein theresilient resistance of said resilient means increases as a function ofthe relative displacement between said arbor means and said clampingcollet member.

12. A workpiece clamping device comprising:

a workpiece support engageable with said workpiece;

arbor means arranged axially of said workpiece and having a firstsurface portion thereon extending parallel to the axis of saidworkpiece;

a clamping collet member having a second surface thereon adapted toengage said first surface on said arbor means, said clamping colletmember further having a first conical surface thereon;

means for causing a relative movement between said arbor means and saidclamping collet member;

a sleeve member having a second conical surface thereon cooperable withsaid first conical surface to cause said clamping collet member toengage said first surface portion on said arbor means, said sleevemember being supported for axial movement relative to said clampingcollet member to cause said clamping collet member to first apply aninitial clamping pressure on said first surface portion on said arbormeans when a relative movement occurs between said arbor means and saidclamping collet member; and

resilient means for causing said sleeve member to resiliently resist therelative movement between said clamping collet member and said arbormeans to cause said clamping collet member to apply a final clampingpressure on said first surface portion on said arbor means.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 664227 Dated May 23, 1972 Inven o Heinrich R. Fischer It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Page 1; please correct the spelling of the name of the Assignee to"Hurth" Signed and sealed this ZL th day of October 1972.

(SEAL) Attest:

' EDWARDTLFLETCHERJR. ROBERT GO'I'TSCHALK Attestlng Officer Commissionerof Patents FORM PO-IOSO (10-69) USCOMM-DC sows-ps9 fl U.S GOVERNMENTPRINTING OFFICE: 1969 0-366-3SA

1. A workpiece clamping device, comprising: a workpiece supportengageable with one end of said workpiece; a movable support member andmeans for moving same toward and away from said workpiece support andengageable with the opposite end of said workpiece; a drawbar and meansfor driving same axially toward and away from said workpiece; clampingmeans on said drawbar for effecting, both an initial and a finalclamping coupling of said drawbar with said workpiece to pull saidworkpiece toward said workpiece support to thereby clamp said workpieceon said workpiece support; and means for resiliently yielding to themovement of said drawbar to delay the application of said final clampingcoupling of said drawbar with said workpiece to thereby permit anadjusting movement of said workpiece relative to said workpiece supportprior to the application of said final clamping coupling.
 2. A workpiececlamping device comprising: a workpiece support engageable with saidworkpiece; arbor means arranged axially of said workpiece; a clampingcollet member adapted to engage said arbor means, said clamping colletmember having a first conical surface thereon; means for causing arelative movement between said arbor means and said clamping colletmember; a sleeve member having a second conical surface thereoncooperable with said first conical surface to cause said clamping colletmember to engage said arbor means, said sleeve member being supportedfor axial movement relative to said clamping collet member to cause saidclamping collet member to first apply an initial clamping pressure onsaid arbor means when a relative movement occurs between said arbormeans and said clamping collet member; and resilient means for causingsaid sleeve member to resiliently resist the relative movement betweensaid clamping collet member and said arbor means to cause said clampingcollet member to apply a final clamping pressure on said arbor means. 3.A workpiece clamping device according to claim 2, including a supportmember and means for moving same toward and away from said workpiecesupport; and wherein said arbor means is secured to said support member.4. A workpiece clamping device according to claim 3, wherein saidsupport member is rotatably secured in a tailstock movable toward andaway from said workpiece support.
 5. A workpiece clamping deviceaccording to claim 2, including means supporting said arbor means forlongitudinal movement relative to said workpiece support; and whereinsaid arbor means is rotatably secured in a tailstock.
 6. A workpiececlamping device according to claim 2, wherein said clamping colletmember has a plurality of angularly spaced slots extending parallel tothe longitudinal axis thereof.
 7. A workpiece clamping device accordingto claim 2, wherein said arbor means includes an enlargement engageablewith said clamping collet member to urge said cooperable conicalsurfaces tightly together to effect a final clamping pressure of saidclamping collet member on said arbor means.
 8. A workpiece clampingdevice according to claim 2, wherein said arbor means is an elongatedextension of said workpiece; and wherein said clamping collet member isadapted to engage said elongated extension of said workpiece.
 9. Aworkpiece clamping device according to claim 8, including an elongatedcentering device supported for axial movement relative to said clampingcollet member.
 10. A workpiece clamping device according to claim 2,wherein said means for causing a relative movement between said arbormeans and said clamping collet member is a drawbar drivable axially ofsaid workpiece; and wherein said clamping collet member is connectedpositively to said drawbar and is movable therewith.
 11. A workpiececlamping device according to claim 2, wherein the resilient resistanceof said resilient means increases as a function of the relativedisplacement beTween said arbor means and said clamping collet member.12. A workpiece clamping device comprising: a workpiece supportengageable with said workpiece; arbor means arranged axially of saidworkpiece and having a first surface portion thereon extending parallelto the axis of said workpiece; a clamping collet member having a secondsurface thereon adapted to engage said first surface on said arbormeans, said clamping collet member further having a first conicalsurface thereon; means for causing a relative movement between saidarbor means and said clamping collet member; a sleeve member having asecond conical surface thereon cooperable with said first conicalsurface to cause said clamping collet member to engage said firstsurface portion on said arbor means, said sleeve member being supportedfor axial movement relative to said clamping collet member to cause saidclamping collet member to first apply an initial clamping pressure onsaid first surface portion on said arbor means when a relative movementoccurs between said arbor means and said clamping collet member; andresilient means for causing said sleeve member to resiliently resist therelative movement between said clamping collet member and said arbormeans to cause said clamping collet member to apply a final clampingpressure on said first surface portion on said arbor means.